Process of obtaining purified iron in the bessemer basic process



UNITED STATES PATENT 'OFF CE.

JACOB EEEsE, OF PITTSBURG, PENNSYLVANIA,

PROCESS OF OBTAINING PURIFIED IRON IN THE BESSEMER BASIC PROCESS.

SPECIFICATION forming part of Letters Patent No. 279,596, dated June 19, 1883.

Application filed January 3, 1882. (No specimens.)

To all whom it may concern:

Be it known that I, J A0013 REESE, a citizen of the United States, residing in Pittsburg, in the county of Allegheny and State of Pennsyl- Vania, have invented a certain new anduseful Improvement-in Processes of Obtaining Purified Iron in the Bessemer Basic Process; and I do hereby declare the following to be a full, clear, and exact description thereof.

In the practice of what is known as the Bessemer process the necessary amount of caloric to keep the metal in ahighly-fluid condition until the close of the blowing operation is developed chiefly by the oxidation of the va rious impurities in the metal, and in some degree by the oxidation of the iron itself as it remains at the close of the blow in an oxidized condition. The temperature developed in the converter therefore will. depend 011 the amount of each of the various impurities present, up on the rapidity of their combustion, the nature of the chemical action which takes place during their combustion, and finally by the absolute heating-power of the various impurities in the metal. In the acid processsilicon is relied upon as the principal caloric-producing element. Therefore not less than one per cent. should be present in order that the metal may be kept in a fluid condition, and not more than two and a half per cent.' should be present, as an excess will cause the'metal to work too hot and boil over. I11 ordinary practice it is desirable to have two per cent. of the weight of the whole charge. In the practice of the basic Bessemer process, however, it was soon discovered that it was desirable to use a metal low in silicon, as the silicic acid formed in the combustion of the silicon is destructive to the basic lining, requires basic conditions in relative amounts to the acid present, and also retards dephosphorization by robbing the phosphate of its base. The difficulties of dephosphorizing such a metal in the lime-lined converter are it must be maintained at a highly-fiuid condition, although it has been robbed of a large'part of its chief caloric-producing agent, and is also robbed of a portion of its caloric by the large basic additions, and thereforein practice it was found that the bath was liable to chill. In order to utilize a metal low in silicon and overcome these difficulties, it was then proposed to desiliconize an ordinary metal in an acid-lined converter, and run the highly-fluid metal into a lime-lined converter, exclude the acid slag, and subject the bath to an overblow. This plan met with better success, as the metal was run into the converter in a highly-heated condition, re-

qui red but small basic additions, and because and fortyeight (448) pounds of silicon present in the metal, and as seven thousand eight hundred and thirty units centigrade of caloric are developed from each pound of silicon consumed -we have three million five hundred and seven thousand eight hundred and forty units centigrade, or 7,830 448:3,507,840 units centigrade from the silicon in the charge. In the use of a metal containing but one-half per cent.

(.5) of silicon by the basic process it will be seen that we only have one hundred and twelve pounds of silicon in a similar charge, and that only eight hundred and seventysix thousand nine hundred and sixty units centigrade will be developed from the oxidation of the silicon; or, in other words, .other things being equal, there will be two million six hundred and thirty thousand eight hundred and eighty (2,630,880) units of heat centigrade less developed on account of the absence of the one and one-half (1%) per cent. of silicon. Now, in order to secure the two million six hundred and thirty thousand eight hundred and eighty (2,630, 880) units centigrade, I substitute a sufficient amount of phosphorus in the metal to develop that amount of caloric during the re fining of the metal. phosphorus is 57 .47 units centigrade, so that it will require (2.05) two and the one-twentieth of one per cent. of phosphorus to be substituted to furnish. an equivalent of caloric for The calorific power of that lost by reducing the silicon in the pig. \Vhen a metal is used containing but a trace of silicon, the amount of phosphorus required to produce an equivalent amount of caloric for that obtained from the oxidation of two per cent. of silicon may be readily computed, thus:

W :611 pounds of phosphorus.

:2.73 per cent. nearly. 22,400

In conducting myimprovement the necessary amount of phosphorus may be had in the metal by smelting phosphoritic iron-ores with coke and limestone in a blast-furnace. In this case the ores should be as low in silica as economically possible, and the limestone addi tions should be in sufficient quantity to give the slag a more basic nature than in the usual practice; or ordinary non-silicious ores should be smelted together with coke and suitable charges of phosphoritic basic slag from the basic converter to flux the metal and charge it with phosphorus to the desired degree, in the manner described by me in a former application; or the metal may be produced in the manner described by me in Letters Patent No. 246,908; or ordinary metal maybe used in con nection with a ferro-phosphide, as described by me in a previous application. In the latter case it is obvious that a metal containing as little silicon should be used as can be conveniently had. XV hen a metal containing the de sired amount of phosphorus is produced, if it contains over one-half (I) per cent. of silicon, I prefer to desiliconize it in a silicious-lined converter and then finish its treatment in the basic converter. If it does not contain over onehalf per cent. of silicon, it may be run direct into a limelined converter. The blast is let on, and the silicon becomes eliminated in from one to two minutes, when the second or decarburizing period commences. The length of this period will vary with the varying amounts of carbon and manganese in different charges, but will generally last from eight to twelve minutes, after which the phosphorus will be rapidly oxidized, the afterblow ranging from one to three minutes.

In this operation it will be found that the quantity of basic additions may be largely de creased, as but little silicic acid is formed, the lime-linings will last longer, the blow will be shortened, the metal will work better and more uniform in the overblow, a better and more regular product can be obtained, and the output will be increased as the use of the two vessels will be avoided.

One advantage of substituting phosphorus for silicon as a heat-producing agent is as follows: In the Bessemer process,when silicon is relied on as the chief caloric-producing agent, the greatest amount of caloric is developed during the first period, while in the basic process it is absolutely necessary to maintain the metal at a very high temperature at the end of the blow, on account of the greater purity of the metal produced; and as phosporus is not oxidized until the silicon and carbon are almost cntirel y removed it produces the greatest heat at the end of the blow, and maintains the metal in ahighly-fluid condition while be ing deoxygenized, recarburized, and cast into the molds.

By the use of the term non-silicious phosphoritic metal I do not wish to be understood as limiting myself to a metal containing no silicon; but refer to a metal in which the silicon has been reduced so far below the normal standard that its presence will not seriously affect the lime-linings, and which contains a sufficient amount of phosphorus to give an increased number of caloric units over that lost by the reduction in the quantity of silicon, so that the metal. may remain in ahighly-fluid condition during the overblow.

It will be observed that a metal of high purity cannot, be produced by the Bessemer acid process because of the impurity of the acid slag in which the metal. is worked; nor, indeed, can this be produced by the basic pro cess per 30. For although the phosphorus may be eliminated, the metal would be so cold and sluggish at the end of the blow that more or less of the slag would be incorporated with the metal; but by diminishing the amount of the silicon and increasing that of the phosphorus the slag is kept more highly basic and pure, and the phosphorus is burned out after the silicon and carbon have disappeared, and this causes the metal to assume a highly-fluid state, so that the carbon, silicon, and phosphorus are entirely eliminated, the slag is separated, and a highly-pnrif1ed metal is pro duced. So', it will be seen. that to secure the object of this invention by the use of the basic process it is necessary that the silicon should be reduced as low as possible, and that sufficient phosphorus should be present in the metal to compensate for the heat-units withdrawn by the reduction of silicon. Although the presence of silicon is injurious in any degree, yet if even two per cent. of silicon is present it can be entirely eliminated if sufficient phosphorus is present to develop the heat necessary to secure a highly-fluid overblow. Therefore, in the use of the term nonsilicious phosphoritic metal I do not intend to limit my invention to a metal which contains no silicon, but rather to a metal contain ing less silicon than phosphorus. In the Bes seiner acid process the metal contains more silicon than phosphorus.

Having described my invention, what I claim, and desire to secure by Letters Patent, 1s

The within-described process for obtaining purified iron in the Bessemer basic process, a basic slag, to the action of an air-blast, sub- Whioh consists, essentially, in smelting phosstantially in the manner and for the purposes phoritio ores low in silicon, in the manner set forth.

substantially as set forth, to obtain non-sili- JACOB REESE. 5 oious phosplioritic metal, and then subjecting Vitnesses:

the resultant phosphoritic metal, while held JAMES H. PORTE,

in a basic-lined converter and in presence of VALTER REESE. 

